In general, a machine tool refers to a machine used for the purpose of processing a metal or non-metal workpiece in a desired shape and size by using various tools by various cutting processing methods or non-cutting processing methods.
The machine tool is generally classified into a turning center and a machining center according to a processing method. Here, the turning center processes a workpiece by rotating the workpiece, and the machining center processes a workpiece by rotating a tool. Accordingly, the machine tool has a spindle device for rotating a workpiece or a tool. Further, the spindles are mounted on a transfer system and transferred in order to process various sizes and types of workpieces.
However, columns supporting the spindles may be thermally deformed by heat generated due to friction of the transfer system and the like during the processing process of the workpiece, and thus location preciseness of the machine tool deteriorates and a defect is generated in a processed good.
In order to solve the problem, a method for compensating thermal displacement illustrated in FIG. 1 is suggested.
Referring to FIG. 1, a compensation quantity is calculated by using temperature data and a predetermined compensation parameter (S110), and the calculated compensation quantity is exponentially smoothed (S120), and the exponentially smoothed compensation quantity is scaled (S130).
Final data obtained by time-dispersion compensation for the scaled compensation quantity (S140) is used as a compensation quantity of each axis of equipment. Here, the time-dispersion compensation is a method of maximizing a processing quality by compensating each axis of equipment by a predetermined compensation unit (1 or 0.1 μm) for each time-dispersion compensating period when the compensation quantity calculated based on the temperature data is changed.
As described above, in the related art, a sharp change in a compensation quantity by noise or ripple of temperature data obtained by a temperature sensor does not influence a surface quality of a processed good, through thermal displacement compensation.
However, the exponential smoothing and the time-dispersion compensation of the compensation quantity essentially cause a time delay, and thus when thermal displacement of equipment is sharply generated, an error between actual thermal displacement and the compensation quantity of the equipment may be generated, and thus an error and the like may be generated in a size of a processed good.
In order to solve the problem, an existing method of performing processing after an error between actual thermal displacement and a compensation quantity of the equipment is sufficiently decreased through a sufficient warming-up time is used, but in this case, there is a problem in that a processing time is increased by the warming-up time.